Tobias acid compositions and diazotization thereof



United States Patent Cecil Arthur Spencer, P lainfield, N. J assignor to American Cyanamid Company, New York,'N. Y., a-corporation of Maine No Drawing. Application September 11, 1956 Serial No. 609,081

6 Claims. Cl. 260-141 This invention relates to improved diazotizable compositions comprising Z-amino-l-naphthalene sulfonic acid (Tobias acid) and to an improved process for diazotization-of the said Tobiasv acid.

Tobias acid is 'an important intermediate for the preparation, of dyes and pigments. For this purpose, it is frequently diazotiz'ed-and coupled with various coupling components. When Tobiasacid is diazotized for subsequent coupling. to form pigments it is desirable that the insoluble diazocompound be produced in the form of fine crystals since this is necessary for best properties of the resulting pigment, as e. g., strength, shade, brightness, etc.

If the diazotization is. not conducted rapidly and the diazo compound immediately. (or within an extremely short time) coupled with the coupling. component the diazo compound crystals increase in size and the resulting pigment is of poor strength .and 'shade. In practice, it is often necessary to complete the coupling within a matter of minutes, otherwise the crystals of the diazo grow to such a size that they areunsuitable'for coupling, and give pigments which are completely unsatisfactory regarding strength-and shade. The crystal growth may be observed visually during the diazotization since if the diazotized mixture is stirred too long before coupling, the crystals reach such a size that they settle to the bottom of the container. This always results in deficient pigments. I

The crystals during formation may also be observed microscopically and the crystalgrowth followed. The diazo crystals, as originally formed, are very small particles. When the growth is followed microscopically, there is observed a very rapid changeto large plates androds.--- It is these large forms which settle rapidly and which couple very poorly with a coupling component such. as beta naphtholw The close control necessary during the diazotization in order to prevent crystal growth and the speed with which it is necessary to work often makes the diazotization operation difiicult tocontroland carry out, especially on large scale operation. Any delay whichcause'sthe mixture to be stirred any appreciable time results in an unsatisfactory pigment.-

The present invention is based onth'e'discovery that, when the diazotization of Tobias acidis carried "out in the presence of an agent stabilizingthe diazo compound against crystal growth, easy control is'possiblefe'ven if the'diazo reaction mixture is stirred excessiveperiods'of time before coupling. It produces high strength pigments with desirable shades.

The suitable crystal growth retarding agents usable in my invention are selected from the-group consisting of polyvinyl alcohol, partially hydrolyzed acrylonitrile, dextrin and polyvinyl pyrrolidonei 'By partially-- hydrolyzed acrylonitrile is meant both polymers which are prepared by hydrolysis of polyacrylonitrile by various means known to the art, those prepared by' hyrolysis of polyacrylamide, polyacrylamide itself and copolymers ice of acrylic acid and acrylamide. The most common form of this class of polymer is a hydrolyzed polyacrylonit'rile, but the expression is meant to include those having up to amide or carboxyl groups, since these-seem to work equally as well as the ones having mixtures of carboxy, amide'and/ or nitrile groups. Hydrolyzed polyacrylonitriles within the above meaning, which have been found operable, include polyacrylic acid, and acrylam'ide, polyacrylamide and hydrolyzed polyacrylonitriles of varying degrees of hydrolysis. These are sold under various trade names such as Carbopol, Cyanomer, Aerofloc, Aeropan and similar names, varying onlyin degrees of hydrolysis and resulting difference in composition. They may also vary in polymer size.

It is an advantage of my invention' that itovercomes the difficulty previously encountered and allows desirable pigments to be obtained even when the time for the diazotization reaction is not' carefully controlled and the mixture is stirred excessive periods of time. In addition, it is a further advantage that it is possible to operate with much larger batches because the time of manipulation is muchless critical.

A further advantage of the invention isth'e ease with which it is possible to destroy any excess nitrite used in the diazotization. Since the stirring time of the diazotization is no longer critical,- when'the agentswe have discovered are used, it is possible to destroy excess nitrite by the addition ofan agent such as sulfamic acid. The extra time-required is nolonger objectionable. For the best results, for example, when coupling with beta naphthol, it is desirable that excess nitrite be destroyed before coupling. since if any excess is present, nitrosobeta naphthol is formed, causing brown shades in the product. It is an advantage of my invention that the excess nitrite can be readily. destroyed without deleterious effects on thepigments.

The process 'of diazotizing Tobias acid inthe presence of the crystal-growth retarding agent, andcompositions comprising Tobiasfa-cid with the crystal growth retarding agents are-both embodiments of the invention. A further embodiment of the invention isthe coupling of the diazo product in the presence ofthe agent to form the'pigment.

- It is most surprising that theparticular types of agents found operable, give such good results and especially when present in only such small amounts. The modifying action of the agent in producing, the improvement is not completely understood since retarding thecrystal growth is not the whole story in producing improved pigments. Even though the crystal growth is retarded,

a deficient pigment can result when the diazo compound is coupled. Various agents are capable of retarding crystal growth to the extent that settling'of the diazo compound is prevented when the diazo mixtureis stirred to an extended period of time, but still result in unsatisfactory pigments when the diazo compound is coupled. Examples of agents which either are noteffec'tive in retarding crystal growth, or retard crystal growth,- but are not eilective in producing superior pigments are: carboxy methyl cellulose, methylated cellulose, hydroxy cellulose, condensation productsof polyoxeth'yle'ne'with tall oil, alginic acid,'zein (partially hydrolyzed protein), tamol (alkylated naphthalene sulfonic acids), sodium meta silicate and glue.

The amount of agent necessary for the improvement is not criticalsinc'e a range" of concentration may be used-from about.*0.05'% to 016% or more, based on the Tobias acid (0.0005 to-.006- par-ts" per part of Tobias acid). For best results, from about 0.2-0.6% is used. More may be used but there is no further improvement and excessive amounts are unnecessary, practically.

The compositions of my invention comprise Tobias parts of water and 3.1 parts of sodium hydroxide.

acid and the stabilizing agent. Various modifiers are also sometimes added to the composition in small amounts (up to about 24% or more in some instances) such as 2-amino-5-chloro-p-toluene sulfonic acid (CTS), naphthyl amine disulfonic acids, l-amino and Z-amino naphthalene sulfonic acids, naphthyl amine methyl sulfonic acids, etc.

To obtain the improvement the Tobias acid may be blended dry with the agent and this then used for diazotization and coupling in the normal way, or the agent may be added to the solution of the Tobias acid at any time before both the acid and nitrite are present. In diazotizing Tobias acid, it is often the practice to dissolve it in caustic solution and then precipitate it in a finely divided form by the addition of a mineral acid, before adding the nitrite; or the nitrite may be added to the caustic solution of the Tobias acid and the mineral acid added to this mixture to elfect the diazotization. The diazo-is then reacted directly with the coupling component. Tobias acid diazo is useful in the preparation of vairous types of pigments. Conmmonly used ones are the calcium, barium, and strontium lakes of Tobias acid diazo coupled With beta naphthol, 2-hydroxy-3-naphthoic acid, or other similar coupling components.

My invention can be further illustrated by the following examples in which parts are by weight unless otherwise specified.

Example 1 A solution of 10 parts of Tobias acid in 70 parts of water containing 2.28 parts of sodium hydroxide is prepared. Ice and water are added to bring the total to about 235 parts and the mixture is cooled to about C. With cooling, 41.95 parts of hydrochloric acid is added with stirring, followed by the rapid addition of 30.3 parts of 10% sodium nitrite solution. The mixture is allowed to stand one hour, and it is then coupled with beta-naphthol solution according to the following procedure. The beta-naphthol solution is prepared by adding 6.7 parts of beta-naphthol to 30 The mixture is heated until the beta-naphthol dissolves, and 10.3 parts of 10% sodium carbonate solution is added. The mixture is made up to about 400 parts with water and 58.8 parts of 8.5% barium chloride solution and 95 parts of rosin solution (21.3 parts of Rosin K in 500 parts of water plus 3.8 parts of sodium hydroxide diluted to 1000 parts with water) are added. The Tobias acid diazo slurry is immediately added with good stirring over a 10 minute period. Stirring is continued an additional 30 minutes and the temperature is raised to the boiling point over the next 40 minutes and held to the boil for minutes. The mixture is cooled to about 85 C. and the solid product is removed by washed and dried. A red pigment is obtained.

The pigment resulting from the above coupling in which the diazotization mixture was allowed to stand was of inferior strength and is practically worthless as a toner. A desirable pigment is obtained, however, if the diazotizatien is carried outrapidly and the resulting diazo is immediately used for coupling without being allowed to stand.

' Example 2 Example 3 The procedure of Example 2 is followed. using polyfiltration,

4 r vinyl alcohol in place of the polyacrylic acid. The result is similar to that of Example 2. Similar results are obtained when polyvinyl pyrrolidone, partially hydrolyzed polyacrylamide, and partially hydrolyzed polyacrylonitrile are used in place of the polyvinyl alcohol. A similar result is obtained when 0.02 part of partially hydrolyzed polyacrylonitrile is used in place of the 0.04 part.

Example 4 One hundred parts of Tobias acid is dry blended with any one of the following agents:

0.6 part polyacrylic acid 0.4 part of polyvinyl alcohol 0.05 part of partially hydrolyzed polyacrylonitrile 0.4 part of yellow dextrin 0.4 part of polyvinyl pyrrolidone The dry blend in each case is dissolved in 700 parts of water containing 22.8 .partsof sodium hydroxide. The solution is then diluted with additional 419.5 water and 419.5 parts of 10% hydrochloric acid is added, followed by the rapid addition of 303 parts of 10% sodium nitrite solution. The mixture is stirred rapidly and then allowed to stand for one hour. In each case, there is little or no settling of solid diazo product and the mixture can be used in the coupling procedure of Example 1 to give a satisfactory pigment.

When the above procedure is repeated using Tobias acid, unblended with any agent, the solid Tobias acid diazo settles within a short time and gives an unsatisfactory pigment on coupling. When the diazotization is carried out using Tobias acid blended with from about 0.2 to 0.6 part of the following agents per parts of Tobias acid, the Tobias acid diazo settles within a short time:

Carboxy methyl cellulose Hydroxy cellulose Zein 3307 (partially hydrolyzed protein) Tall oil condensate with polyoxyethylene of from 2 to 32 ethylene units Alginic acid Sodium meta silicate Glue Such diazos also give unsatisfactorypigments on coupling. Q

I claim: a r

1. In the process for the diazotization of 2-aminonaphthalene-l-sulfonic acid, the improvement which comprises diazotizing in the presence of at least 0.0005 part, per part of said amino naphthalene sulfonic acid of an agent selected from the group consisting of polyvinyl alcohol, dextrin, polyvinyl pyrrolidone and hydrolyzed polyacrylonitriles.

2. The process-of claim vinyl alcohol.

3. The process of claim 1 in which the agent is dextrin.

4. The process of claim 1 in which the agent is a polyvinyl pyrrolidone.

5. The process of claim 1 in which the agent is a hydrolyzed polyacrylonitrile.

6. The process of claim 5 in which the hydrolyzed polyacrylonitrile has principally carboxy and amide side chains.

1 in which the agent is poly- References Cited in the file of this patent UNITED STATES PATENTS 650,757 Julius May 29, 1900 FOREIGN PATENTS j 439,550 ,Great Britain i936 

1. IN THE PROCESS FOR THE DIAZOTIZATION OF 2-AMINONAPHTHALENE-1-SULFONIC ACID, THE IMPROVEMENT WHICH COMPRISES DIAZOTIZING IN THE PRESENCE OF AT LEAST 0.0005 PART, PER PART OF SAID AMINO NAPHTHALENE SULFONIC ACID OF AN AGENT SELECTED FROM THE GROUP CONSISTING OF POLYVINYL ALCHOL, DEXTRIN, POLYVINYL PYRROLIDONE AND HYDROLYZED POLYACRYLONITRILES. 